Numerical analysis of the effect of pre-precipitation of foundation pits on adjacent group piles

Pre-precipitation before excavation of the foundation pit will cause the displacement of the surrounding soil, which will affect the adjacent group piles in turn. Based on the foundation pit engineering of a station in Nanchang Metro Line 4, this paper establishes a three-dimensional fluid-solid coupling model of the influence of pre-dewatering on adjacent group piles with the help of PLAXIS 3D finite element software, studies the settlement pattern of the ground surface outside the pit and the mechanism of force deformation of the adjacent piles under the pre-dewatering condition, and further analyzes the influence of the pile length and pile diameter on the stress and deformation of the pile foundation. The calculation results show that the vertical displacement distribution of the surface outside the pit caused by precipitation is “spoon-shaped”, and the existence of the adjacent piles will hinder the displacement of the surrounding soil. The vertical displacement of the pile foundation gradually decreases with the increase of the pile depth and distance from the pit. When controlled variables are used, the increase in pile length and pile diameter leads to an increase in the ability to resist the surrounding soil displacement and a decrease in vertical displacement. Especially as pile diameter increases, the range of variation in vertical displacement of the pile foundation decreases significantly. The maximum axial force of the pile foundation tends to increase with the pile length or pile diameter increasing, and the position of the neutral point also moves downward due to its influence.